As disclosed in PTL 1 below, in recent years, multi-component content including a plurality of components such as video, audio, and text has been distributed.
Here, in reception and reproduction of such a multi-component content, composition information indicating a usable component, its reproduction mode, and the like is required. Therefore, it is necessary for a reproduction device to acquire the composition information of content to be reproduced together with each component or independently from the component.
For example, in MPEG MMT (MPEG Media Transport), composition information (CI) is distributed together with a component and a reproduction device reproduces the component with reference to this composition information.
For example, in MPEG-2 systems (ISO/IEC 13818-1), information corresponding to composition information called PAT/PMT (Program Association Table/Program Map Table) is multiplexed with each component and is repeatedly distributed. Specifically, in terrestrial digital broadcasting, composition information is distributed normally at intervals of 100 msec in order to minimize reproduction start delay at the time of channel conversion.
For example, SDP (Session Description Table) of RFC 4566 or MPD (Media Presentation Description) of MPEG DASH (ISO/IEC 23009-1) also corresponds to the foregoing composition information. Such information is distributed on demand asynchronously with components through communication independent from the components.
Here, composition information and components included in content of MPEG MMT will be described with reference to FIG. 16. FIG. 16 is a diagram for describing the components and the composition information in MPEG MMT. FIG. 16(a) illustrates a distribution example of the components and the composition information and FIG. 16(b) illustrates an example of the composition information.
In FIG. 16(a), each component and each piece of composition information are indicated as one block. In FIG. 16(a), a distribution time of the components and the composition information are shown in chronological order. The components indicated by dashed lines are components to be optionally reproduced.
That is, in FIG. 16(a), eight kinds of components c1 to c8 are transmitted. Of the components, the components c1 to c4 are distributed during the same period and the components c5 to c8 are distributed during a later period than the period.
As a specific example, the component c1 may be a component of a moving image and the component c2 may be a component of audio corresponding to the moving image. Further, the component c3 may be a component of English subtitles corresponding to c1 and c2 and the component c4 may be a component of French subtitles.
Likewise, the component c5 may be a component of a moving image and the component c6 may be a component of audio corresponding to the moving image. Further, the component c7 may be a component of English subtitles corresponding to c5 and c6 and the component c8 may be a component of French subtitles.
In this case, a scene including the components c1 and c2 is reproduced, and then a scene including the components c5 and c6 is reproduced. In the scene including the components c1 and c2, English or French subtitles can be displayed by using the component c3 or c4. The same applies to the scene including the components c5 and c6.
As illustrated in FIG. 16(a), composition information (CI) is repeatedly distributed at regular intervals. The details of all pieces of composition information are the same and have, for example, details illustrated in FIG. 16(b).
The composition information in FIG. 16(b) includes information regarding an attribute of a component described by a <components> tag (information indicating a component included in content) and information regarding a reproduction method (reproduction mode) described by a <compositions> tag.
Specifically, in the <components> tag, eight components from a component with an id of “c1” to a component with an id of “c8” are described.
In the <compositions> tag, it is described that c1 which is a video component and c2 which is audio component are simultaneously reproduced. Further, it is described that any one of c3 and c4 which are text components can be selected and used. The same description is made for the components c5 to c8.
Accordingly, a reproduction device reproducing these components first acquires the distributed components c1 and c2 and acquires the repeatedly distributed composition information. The components c3 and c4 are also acquired, as necessary.
Thus, the reproduction device simultaneously reproduces the components c1 and c2 according to the composition information and uses the component c3 or c4 during the reproduction, as necessary.
Thereafter, the reproduction device acquires the components c5 and c6 distributed after the components c1 and c2 and also acquires the component c7 or c8, as necessary. Thus, the components c5 and c6 are simultaneously reproduced according to the composition information and the component c7 or c8 is used during the reproduction, as necessary.
In this way, by transmitting the composition information, a plurality of components can be reproduced in an appropriate combination. By describing a display layout or the like representing a component reproduction mode in the composition information, for example, the component can also be reproduced in a certain layout.